The present invention relates to an exposure method. More particularly, the present invention relates to an exposure method for exposing a flat substrate to a pattern for fabricating a liquid crystal display panel, a plasma display panel, and the like.
Display qualities of recent liquid crystal display panels and plasma display panels are remarkably enhanced. Moreover, the liquid crystal display panels and the plasma display panels are thin and light, and thus are becoming major image display apparatuses as substitutes for CRTs. Particularly, a direct-view type active matrix liquid crystal panel is making progress in enlarging its screen size, and to that end the size of glass substrates used for fabricating the liquid crystal panels are becoming larger as well.
As an exposure method for exposing a large-sized glass substrate to element patterns of a display panel, a scanning-type exposure method is known. According to the scanning-type exposure method, exposure is performed by synchronously scanning a photomask or a reticle having a pattern formed thereon (hereinafter, referred to as a xe2x80x9cmaskxe2x80x9d) and a glass substrate applied with a photosensitive agent such as a photoresist (hereinafter, referred to as a xe2x80x9csubstratexe2x80x9d).
As an example, scanning exposure of a substrate to a mask pattern at one to one magnification will be described. Assume that the size of an effective exposure area of the mask is 400 mmxc3x97700 mm, the size of the substrate is 720 mmxc3x97900 mm, and the size of a substrate holder for carrying the substrate is 843 mmxc3x97890 mm. A scanning-type exposure apparatus, which synchronously transfers a mask stage (for supporting and transporting a mask) and a substrate stage (a substrate holder for supporting a substrate) with respect to a projection optical system, is used to expose a substrate to a pattern of a 17-inch SXGA liquid crystal display panel. The size of the 17-inch SXGA panel including a circuit pattern surrounding a pixel region is 279.7 mmxc3x97347.2 mm.
The size relationship is shown in FIGS. 7 and 8. FIGS. 7 and 8 are schematic views showing the sizes of a rectangular substrate holder 15a and a substrate 200 held by the substrate holder 15a (which is represented by dotted lines in FIG. 8 for distinction from the substrate 200), respectively. As shown in FIG. 8, the substrate 200 is loaded on the substrate holder 15a such that the longer sides of the substrate 200 are arranged along the longer sides of the substrate holder 15a. 
FIG. 9 is a schematic view for illustrating a manner of printing six 17-inch SXGA panels on the above-described substrate by using a mask 100 that has two 279.7 mmxc3x97347.2 mm circuit patterns 101 formed thereon. In FIG. 9, the substrate holder 15a is omitted.
With reference to FIG. 9, an exposure of patterns of 17-inch SXGA liquid crystal display panels is carried out as follows. First, a first scanning exposure is conducted by synchronously transferring the mask 100 and the substrate 200 in the X-direction as indicated by an arrow 1 to print two circuit patterns 101 on exposure areas 200a and 200b of the substrate 200.
Then, the mask 100 and the substrate 200 are transferred back to the exposure initiating positions to perform a second scanning exposure to print a single circuit pattern 101 on an exposure area 200c as indicated by an arrow 2. Since the length of the side of the substrate 200 is 900 mm, two circuit patterns 101 cannot be exposed at the second scanning exposure.
Next, while the substrate 200 is step transferred in the Y-direction, the mask 100 and the substrate 200 are transferred back to the exposure initiating positions to perform a third scanning exposure to print a single circuit pattern 101 on an exposure area 200d of the substrate 200 as indicated by an arrow 3. Finally, two circuit patterns 101 are printed on exposure areas 200e and 200f as indicated by an arrow 4.
According to such a conventional exposure method, even when the mask 100 is provided with two circuit patterns 101, there is a case where only a single circuit pattern 101 can be printed at a time. As a result, the number of scanning exposure increases, limiting improvement of the throughput.
In view of the current situation of scanning exposure, the present invention has an objective of providing an exposure method which can be carried out with reduced number of scanning steps and at enhanced throughput.
According to the present invention, the above-mentioned objective is achieved by allowing a substrate to be placed in sideways (rotated by 900) with respect to a substrate holder (placing the longer sides of the substrate in parallel to the shorter sides of the substrate holder) depending on the size of the apparatus and the size of the substrate. When the substrate is placed in sideways with respect to the scanning direction, or the substrate holder, it is acceptable even when areas other than an effective exposure area of the substrate should project out from the substrate holder, since there is no need of precisely controlling flatness of areas of the substrate where they are not exposed to a pattern.
Along with the reference numerals, the present invention is an exposure method for exposing a rectangular substrate (14) to a pattern (30a) of a mask (30) by transferring a mask stage (20) carrying a mask (30) formed with the pattern (30) and a rectangular substrate holder (15a) carrying the substrate (14) in a first direction (X-direction), the method comprising: a step (S22) of placing the substrate (14) whose longer sides are longer than the shorter sides of the substrate holder (15a), on the substrate holder (15a) such that the longer sides of the substrate (14) are generally arranged along the shorter sides of the substrate holder (15a); a step (S25) of exposing a first area (14a, 14b) of the substrate (14) to the pattern (30a) of the mask (30) by transferring the mask stage (20) and the substrate holder (15a) in the first direction (X-direction); a step (S26) of transferring the substrate holder (15a) in a second direction (Y-direction) which is generally perpendicular to the first direction (X-direction); and a step (S27) of exposing a second area (14c, 14d) of the substrate (14), which is adjacent to the first area (14a, 14b) along the second direction (Y-direction), by transferring the mask stage (20) and the substrate holder (15a) in the first direction (X-direction).
According to the exposure method of the present invention, the number of scanning steps can be reduced, thereby realizing high throughput.
The exposure method of the invention can comply with the recent tendency toward enlargement of the substrate size, and can be applied without enlarging the exposure apparatus. For example, the exposure method of the invention is applicable to a substrate whose shorter side is 680 mm or longer and whose longer side is 880 mm or longer.
The first direction (X-direction) may be parallel to the longer sides of the substrate holder (15a). The first (14a, 14b) and second (14c, 14d) areas are positioned in a region where the substrate (14) is making contact with the substrate holder (15a). Alignment marks are preferably formed in a region where the substrate (14) is making contact with the substrate holder (15a).